Pulmonary function test

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• Pulmonary function test
• Part II
• Dr.Mona AL-Langawi
• Consultant Pulmonary/Allergy
• Hamad General Hospital - HMC

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• Pulmonary function test
• Spirometry
• Lung volumes
• Gas transfer
• Bronchial challenge

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• 
  
  
  1.Volume Time Graph
• FVC
• FEV1
• FEV1/FVC
• FEF25
• FEF75
• FEV1 80 Normal
• FEV1 60-80 mild obst. 2.
  Flow-volume loops
• FEV1 40-60 moderate
• FEV1 40 severe
• The cardinal feature is FEV1/FVC ratio If
• lt70 consider obstructed
• Predictors Sex, Age, Ht
• 
  
• 
  

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Interpretation of Spirometry

• Step 1. Look at the Flow-Volume loop
• Step 2. Look at the FEV1 (Nl 80 predicted).
• Step 3. Look at FVC (Nl 80).
• Step 4. Look at FEV1/FVC ratio (Nl 70).
• Step 5. Look at FEF25-75 (Normal ( 60)

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• If FEV1, FEV1/FVC, and FEF25-75 all are normal,
  the patient has a normal PFT.
• If both FEV1 and FEV1/FVC are normal, but
  FEF25-75 is 60 ,then think about early
  obstruction or small airways obstruction.
• If FEV1 80 and FEV1/FVC 70, there is
  obstructive defect, if FVC is normal, it is pure
  obstruction. If FVC 80 , possibility of
  additional restriction is there, get lung volume
  to confirm.
• If FEV1 80 , FVC 80 and FEV1/FVC 70 ,
  there is restrictive defect, get lung volumes to
  confirm.

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• Acceptability Criteria
• free from artifacts
•  Cough or glottis closure during the first second
  of exhalation
• Eary termination or cutoff
• Variable effort
• Leak
• Obstructed mouthpiece
•  Have good starts
• Have a satisfactory exhalation 6 s of exhalation

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• Reproducibility Criteria
• After 3 acceptable spirograms been obtained
• Are the two largest FVC within 200ml of each
  other?
• Are the two largest FEV1 within 200ml of each
  other?
• If both of these criteria are met, the test
  session may be concluded.
• If both of these criteria are not met, continue
  testing until Both of the criteria are met with
  analysis of additional acceptable spirograms OR
  a total of eight tests have been performed

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• Pulmonary function test
• Group of procedures that measure the function
• of the lungs
• Spirometry
• Lung volumes
• Gas transfer
• Bronchial chalenge

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• Lung volumes

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• Indication for lung volume test
• Low FVC
• -? Restrictive
• -? Obstructive with hyperinflation and air
  trapping
• -? Mixed pattern
• -? Equivocal spirometry findings (FEV1FVC at
  lower limit of normal)

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• Measurment of lung volumes requires a
• method of estimating the volume of gas inside
• the thorax
• The most common methods of assessing lung volumes
  are
• 1. Gas dilution tests.
• 2. Body plethysmography (Body Box).

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• 1.Gas dilution tests
• Lung volume can be measured when a person
  breathes nitrogen or helium gas through a tube
  for a specified period of time.
• The final dilution of the gas used to
  calculate the volume of air in the thorax.
• Helium doesnt readily diffuse across the
  alveolar capillary membrane .
• It is sensitive to errors
• Leakage of gas
• Failure to measure the volume of gas in lung
  bullae.because helium may not mix with all parts
  of the lung .

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2.Body plethysmography

• The most accurate way
• The patient sits inside a fully enclosed rigid
  box and breath through mouthpiece connected
  through a shutter to the internal volume of the
  box
• The subject makes respiratory efforts against the
  closed shutter (like panting), causing their
  chest volume to expand and decompressing the air
  in their lungs.
• while breathing in and out again into a
  mouthpiece. The volume of all gas within the
  thorax can be measured by Changes in pressure
  inside the box and allow determination of the
  lung volume.

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• Using the data from the plethysmography requires
  use of Boyles Law.

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• By this technique we will be able to know
• Residual volume (RV)
• Tidal volume (TV)
• Total Lung Capacity (TLC)
• Expiratory reserve volume (ERV)
• Inspiratory Reserve Volume (IRV)
• Inspiratory capacity (IC)
• Functional residual capacity (FRC)
• Vital Capacity (VC)

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Residual volume (RV) It is the volume of air
remaining in the lungs at the end of maximal
expiration. Normally it accounts for about 25 of
TLC. - RV increased in airway narrowing with
air trapping (B.Asthma) or
in loss of elastic recoil (emphysema).- RV
decreased in Increased elastic recoil (pulmonary
fibrosis)
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Tidal volume (TV) It is the volume of air
inspired or expired with each breath during
normal breathing ( 7ml/kg) 400-700mlTV decreased
in severe RLD
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Total Lung Capacity (TLC)It is the total
volume of air within the lung after maximum
inspiration. (the maximum volume of air that the
lung can contain). TLC FVC RV OR TLC RV
ERV TV IRVTLC Increased in airway
narrowing with air trapping (B.Asthma) or
in loss of elastic recoil
(emphysema). TLC Decreased in RLD , increased
recoil (Pulmonary fibrosis), muscle weakness,
Obesity
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Expiratory reserve volume (ERV)It is
the maximal volume of air exhaled from the
resting end-expiratory level. ( volume expired by
active expiration after passive expiration.ERV
From TV to RV ERV decreased in RLD
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Inspiratory Reserve Volume (IRV)It is
the maximal volume of air inspired with effort in
excess of tidal volume IRV From TV to TLC
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Inspiratory capacity (IC) It is the
maximal volume of air inspired from resting
expiratory level IC IRVTV.
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Functional Residual Capacity (FRC) It is the
volume of air remaining in the lungs at the end
of resting (normal) expiration. FRC RV
ERV.-FRC Increased (gt120 of predicted) in
Emphysema (decreased elastic recoil), B.Asthma,
bronchiolar obstruction (air trapping)-FRC
decreased in intrinsic ILD or by upward movement
of diaphragm (obesity,painful thoracic or
abdominal wound)
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Vital Capacity volume of gas measured on
complete expiration after complete inspiration
without effortVC TLC RV or VC
IRVTVERVdecreased in OLD and RLD( VC lt 15
ml/kg (and VT lt 5ml/kg) indicates likely need for
mechanical ventilation
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Lung volumes capacities
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• Lung Volume in
• Obstructive Lung Disease

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• Obstructive Lung Disease
• Narrowing and closure of airways during
  expiration tends to lead to gas trapping within
  the lungs and hyperinflation of the chest.
• Air trapping ? increase in RV
• Hyperinflation ? increases TLC
• RV tends to have a greater percentage increase
  than TLC
• RV/TLC ratio is therefore increased (nl 20-35)
• Gas trapping may occur without hyperinflation
  (increase in RV normal TLC)

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• Gas trapping and airway closure at low lung
  volume cause the patient to breath at high lung
  volume so FRC (RVERV) increased
• This will prevent airway closure and improve
  ventilation-perfusion relationship
• It will reduce mechanical advantage of
  respiratory muscles and increases the work of
  breathing

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• Obstructive Lung Disease cont.
• RV increased
• TLC Nl/increased
• RV/TLC increases
• FRC increased
• VC decreased
• Air trapping Normal TLC with
• increase RV/TLC
• Hyperinflation Increase in both
• TLC and RV/TLCl/

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• Lung Volume in
• Restrictive Lung Disease

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• Reduction in TLC is a cardinal feature
• 1. In Intrinsic RLD (Interstitial Lung Disease)
• TLC will decrease
• RV will decrease because of increased elastic
  recoil (stiffness) of the lung and loss of the
  alveoli.
• Breathing take place at low FRC because of the
  increased effort needed to expand the lung .
• RV/TLC normal

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• 2. In extrinsic RLD (chest wall disease
  kyphoscoliosis or neuromuscular diseaseALS,MG)
• TLC is reduced either because of mechanical
  limitation to chest wall expantion or because of
  respiratory muscle weakness
• RV is Normal because Lung tissue and elastic
  recoil is normal
• So RV/TLC ratio will be high
• Breathing take place at low FRC because of the
  increased effort needed to expand the lung .

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• Restrictive Lung Disease
• RLD Intrinsic severe chest
• wall dis (pleural and skeletal)
• TLC decreased
• RV decreased
• RV/TLC normal
• FRC decreased
• VC decreased
• Extrinsic RLD
• TLC decreased
• RV normal
• RV/TLC High
• VC decreased
• FRC decreased

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• 3. In combined obstructive and restrictive
  disease(e,g.sarcoidosis ,COPDIPF)
• Obstructive pattern on spirometry and
• Reduced lung volume
• 4. In equivocal spirometry result
• e,g.when FEV1,FVC at lower limit of normal
• If TLC or RV raised the diagnosis is obstructive
• lung disease

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• Example

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• Flow vloume loop suggestive obstructive defect
  with feature of Dog-Leg appearance
  (characteristic of Emphysema)
• Severe irreversible obstructive defect with
  airtrapping and hyperinflation
• Diagnosis
• Emphysema